Abstract :
[en] In Escherichia coli, penicillin-binding protein 3 (PBP3), also known as FtsI, is a central component of the divisome, catalyzing cross-linking of the cell wall peptidoglycan during cell division. PBP3 is mainly periplasmic, with a 23 residues cytoplasmic tail and a single transmembrane helix. We have solved the crystal structure of a soluble form of PBP3 (PBP357-577) at 2.5 Å revealing the two modules of high molecular weight class B PBPs, a carboxy terminal module exhibiting transpeptidase activity and an amino terminal module with unknown function. To gain additional insight, the PBP3 Val88-Ser165 subdomain (PBP388-165), for which the electron density is poorly defined in the PBP3 crystal, was produced and its structure solved by SAD phasing at 2.1 Å. The structure shows a three dimensional domain swapping with a β-strand of one molecule inserted between two strands of the paired molecule, suggesting a possible role in PBP357-577 dimerization.
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